This invention relates to dynamoelectric machines such as large turbine generators and particularly to the stator coil end turn support systems thereof.
The description contained in Dailey et al. U.S. Pat. No. 4,379,243, Apr. 5, 1983, is herein incorporated by reference. The patent discloses an end turn support structure that has a conical member located radially outside the end turns. It provides a support structure that has thermal expansion characteristics so it expands in a manner similar to the end turns which it supports. In structures so made, the conical member and a top and a bottom coil of an end turn are secured together by bolts or studs extending from the outside of the conical member through a support ring that is located inside the top coils of the end turns. The stud necessarily passes adjacent to the top and bottom coils. As thus arranged, the original manufactured assembly can be made quite secure but a need exists to make sure the assembly is not only secure and able to withstand the forces to which it is subjected in operation as originally manufactured, but also that there is a way to easily adjust the tightness of the assembly after a period of operation, while it remains in the field, in order to account for creep and shrinkage of the insulation materials employed in the assembly. A degree of adjustability of the prior structure is attained by the threaded stud but such an element requires a clearance substantially beyond that of the top and bottom coils themselves. Its use is limited to the portion of the end turn proximate its axial extremity because the inboard region of the end turn has limited space between it and the rotor. Thus, the extending stud would either be totally unusable or would be so limited in its access that it could not be retightened in the field while the rotor of the machine is in place.
The present invention has primarily to do with making a secure end turn support region which allows greater support of the coils by a conical support member while also permitting greater facility of adjusting the tightness of such a support over the entire end turn length. The invention also has to do with a structural arrangement for insuring the conical support member against rotation forces.
In order to tighten the coils to the conical support member, the present invention utilizes a system of radial banding. The radial banding is applied at one or more spaced locations along the axial length of the end turn. It may be used in addition to the former threaded stud assembly of an inner support ring and the conical member which is located proximate the axial extremity of the end turn. In a particular embodiment, such a threaded stud is employed near the axial extreme of the end turn and at two spaced locations along the end turn closer to the core of the machine there is applied the radial banding of the coils and the conical member.
The radial banding is substantially a banding of a high strength material such as a glass fiber reinforced, resin impregnated banding material, which encompasses the top and bottom coils at a particular end turn location and also passes through apertures in the conical support member. Additionally, however, there is provided means for the adjustment of the banding tightness. This comprises, in a specific embodiment, an adjusting ring that is located radially within the top coils at the banding location. The adjusting ring has a surface that fits against the top coil surface and it also has a portion that projects away from the top coil. The portion projecting away from the top coil has an aperture therein through which is fit a fastener secured to a wedge that conformably fits on top of the portion of the adjusting ring against the coil. The wedge also has a banding block located on its surface away from the coil and it is on the banding block itself that the banding material is applied in assembly. The wedge disposed between the adjusting ring and the banding block permits tightening of the banding during initial assembly as well as in the field in operation. The fastener to which the wedge is attached is threaded on its axially outer portion. A nut on the threaded fastener can be reached, even if the rotor is in place, to draw the wedge axially outward, forcing the banding material to tighten against the banding block. The assembly may include a plurality of disc-shaped spring washers to help insure the fastener remains tight.
The advantages of this arrangement include easy adjustability in the field as well as during original manufacture, the adjusting nut on the fastener of the adjusting device is accessible from the axial extreme of the machine, the adjusting device has a relatively low profile so that it fits readily within the space available between the top coil and the rotor structure, and the adjusting ring also provides a way to compress the structure before the hoses are pressurized that extend between the top and bottom coils of the end turns.
Another aspect of the invention is that the conical support element is configured with projections on its axial inmost extreme and such projections fit within apertures provided in the core so that the cone is not susceptible to rotation during operation.